Basic J group

The black shape in the diagram is the basic J group. It has the same status as an L+1 group: it lives or dies according to who has sente. This basic shape is known in China as the Big Pig's Snout.

White kills

The correct way for White to kill this shape looks like a complete display of the principal killing techniques: reducing the eye space with a hane at , followed by a placement on the vital point at , followed by a descent at and a throw-in at . The order of and is interchangeable.

The best way for Black to live is by playing at , giving him six points of territory.

Straight J group

Straight J group

Black can improve on the status of his corner by descending to the edge instead of making a hanging connection. The best White can do now is turn the corner to ko (though White also has the option to unconditionally snip off the two
lower black stones leaving the main Black group alive, which might be better in rare cases).

Ko 1 - White captures first

There are several good ways to produce a ko and one less good way. A representative good variation is shown. 1 can be at a, or with 1 as shown, 3 can be at 5 or a, each giving a more-or-less equally good result with White getting to make the first ko capture.

ko 2 - Black captures first

This way of setting up a ko is less good. It only works when the black group has no external liberties and Black gets to make the first ko capture (though if White wins the ko, she removes a part of the black group from the board).

Mistake

Failure to make a hane before making a placement at is a mistake. to lives with two eyes.

Straight J group with an outside liberty

Avoiding ko

[100] If Black has an outside liberty, the second ko doesn't work because he can live by answering this way. He sacrifices two stones and plays at .

Avoiding ko (2)

Black is alive in sente for an average gote endgame by white. This result is very favourable for black over being killed straight. If Black had expected 6 points in the corner - he needed to defend the two stones and against the hane - he now has 4 points (B = -2). White on the other hand made 4 points by the two-stone capture (W = +2). As a net loss of six points (B = -2 -4), Black gains hugely in this exchange for not playing gote twice. White might think in terms of "I made 6 points", but she has to realize that she lost around 13 (approx. 19 for capturing the group minus 6 points) points by starting with the wrong move.

The liberty

When there is no extra outside liberty, as here, instead of a keeps Black short of liberties. Black can't play at b now and must play for the ko.

Ko 1

All 'good' variations of the first ko from the previous section still work with the extra outside liberty.

Discussion

has an alternative in special cases

Life and death evaluation of shapes is normally done without the ability to escape. Look at the funny white 'wings' on the outside of the L-group in the first diagram of L Group. Even the L-group is alive in sente if descending to either edge is a threat to escape.

The present shape would normally be studied/evaluated with a white stone at b to prevent such an escape. In such a case (no escape) finishes off Black. In studying life and death, then, we need to learn the basic techniques. Next, memorization of the fundamental cases can be a powerful tool to improve play in real games.

However, as much as the vital points and main continuations, we need to thoroughly understand the various conditions such as no escape, no/limited outside liberties, relationship to the corner, etc. that may apply to each case. Small differences in game situations can turn around any of the proverbs/rules of thumb that we have studied so hard!

That's why I try to teach fellow beginners the merit of a net above a ladder. The ladder is a non-local move versus a local move: you need to look at more parts of the goban. Ladders may be easier to pattern-match; sure - but a ladder's status changes more rapidly than a net's.

Andy: If the Straight J group is more robust than the Basic J group, because the Straight J is ko if the opponent plays first while the Basic J is dead if the opponent plays first, why ever make the Basic J group? Are there advantages the Basic J has over the Straight J, and could those be explicitly listed on this page please?

fw280?: We make J group instead of straight J, when we have hane. Because J group with hane is better than straight J.